High-tech applications can be found in almost all industrial sectors, for example in semiconductor manufacturing, medical technology or in the agricultural, printing and aerospace industries. Precise positioning systems usually consist of a drive component and a driven unit. The coupling performs the power transmission function. In order to select a backlash-free coupling for drive technology that meets the requirements, it is first necessary to gain an overview of the strengths and weaknesses of individual coupling types.

Rigid couplings, also known as shell couplings, are available in various materials and designs. For high-tech applications, the clamp design is more suitable than the set screw design as they do not cause damage to the shaft and have higher torque capabilities. Rigid couplings have the highest possible rated torsional stiffness and are therefore ideal for high-tech applications with precise motion sequences and small work steps, such as 3D printers.

Compared to other couplings, the bearing load is highest with rigid couplings. The shafts must be perfectly aligned. At high speeds, thermal expansion must also be taken into account, as rigid couplings cannot compensate for the resulting stresses.

Clutch types for high speeds in semiconductor and printing technology

Multi-plate clutches consist either of two hubs that are connected via a flexible, metal center disc (single-joint design) or of two hubs and a center piece in which two metal plates provide the connection (double-joint design). The latter can accommodate parallel and angular misalignments. Multiple-disc couplings in single-joint design are intended for smaller installation spaces and only compensate for angular misalignments.

Both variants are torsionally rigid, result in low bearing stress and have a low mass moment of inertia. The flexible disks make it possible to compensate for larger shaft misalignments, especially in the double-jointed version. Multi-plate clutches are suitable for applications up to 10,000 ^rpmand beyond. These features make them the perfect choice for semiconductor and solar applications.

Bellows couplings consist of two aluminum or stainless steel hubs that are connected to each other via a metal bellows. The thin walls of the stainless steel, bronze or nickel bellows give the coupling a dynamic response and high precision. The bearing load is low and constant at all points of the rotary movement. Bellows couplings can compensate for all types of misalignment.

In addition to all these advantages, the bellows coupling has excellent torsional stiffness. The maximum speed of around 10,000 ^rpmalso corresponds approximately to the performance of a multi-plate clutch. It is particularly suitable for the printing industry, where maximum precision is required to avoid streaking on printed copies.

Non-positive clutches for start-stop operation and precise regulation

The backlash-free elastomer coupling, also known as a claw coupling, has rounded hub and claw profiles. It consists of three frictionally connected parts, i.e. two aluminum hubs and a star-shaped elastic connecting element, also known as a star or spider. Thanks to their high damping properties, elastomer couplings with rounded profiles are ideal for inspection systems with start-stop operation.

Like an elastomer coupling, the Oldham coupling also consists of three friction-locked components, namely two aluminum hubs and an insert. The couplings compensate for large parallel displacements with low bearing loads, the center disc is easily replaceable and they act as a mechanical safety device in the event of torque overload. Oldham couplings are used, for example, in valve control applications where particularly precise regulation is required. These types of clutch can only compensate for small angular displacements and axial movements. Their speed range extends up to around 4500 ^min-1.

Performance and durability thanks to the right clutch in the right place

The performance of high-tech applications depends largely on the performance and quality of the respective components. All the clutch types described have design-related strengths and weaknesses. There is no coupling that can cover the requirements of all systems and applications.

In any case, it is advisable to select the correct backlash-free clutch in the initial phase of system development based on all available data. Only the selection of a coupling whose functional characteristics fulfill all system requirements can ensure the best possible system performance and longevity. am